The present invention relates to the disposable products industry, particularly to the field of manufacturing disposable undergarments.
Consumer demand for disposable undergarments such as diapers or panties has continued to grow since these items were introduced in the market. These products are used on children who are not yet toilet trained, as well as on adults who are fully or partially incontinent due to illness or other medical conditions. Disposable undergarments, diapers and panties in particular, are usually fabricated of at least three layers of material: a barrier bottom layer impervious to liquid; a top porous layer which touches the skin of the wearer and freely allows liquids to pass through; and an inner layer of an absorbent material, positioned between the top and bottom layers for holding fluids discharged by the wearer.
There has been interest in applying emollient preparations and various other products such as creams and petroleum jelly to the layer of the disposable undergarment which goes against the wearer""s skin. These products may include creams to fight diaper rash, emollients to aid in keeping the wearer""s skin soft, lubricants to help prevent stools from adhering to the skin, antibiotic preparations to control and suppress infections, and others. The application of such products, which are usually soft, cream-like, or jellied preparations, however, poses a technical challenge in the manufacturing process. Generally, these products are semisolid gels or creams which may be difficult to convey and to apply onto materials moving on a production line. This is particularly true since these soft preparations must be applied to the top layer of the undergarment, so that they will contact the skin of the wearer. For the undergarment to maintain its effectiveness, however, the top layer of the undergarment, which is next to the skin of the wearer, must remain permeable to liquids and cannot be blocked by the application of the gel preparation. Techniques which are well known in the art for applying a gel during the manufacturing process include spraying and deposition through an applicator shoe.
In one known application technique the gel preparation is sprayed onto the material moving on the production line. In order to spray a gel, however, the gel must be heated to the point that it turns liquid. This heating tends to cause some evaporation of the gel and to affect the consistency of the gel upon cooling; the gel becomes harder as more liquid evaporates during this process. In addition, controlled deposition of gel onto the material moving on the production line is difficult when using a spraying process. Spray, particularly a hot spray, tends to spread during application and to run uncontrollably over the material once deposited; this tends to cover the entire surface of the material with liquefied gel. Because the spray covers most of the surface of the material, as the spray cools and the gel forms once again, most of the pores on the material will be clogged with gel and the undergarment""s absorbency will be greatly reduced. The undergarment will be less comfortable to the wearer because of its reduced absorbency.
In another known technique the gel may be applied onto the material moving on the production line by deposition through an applicator shoe. This method is well known in the art of manufacturing disposable undergarments. Present applicator shoe designs, however, also tend to spread the gel over most of the surface of the undergarment material. The gel is deposited across most of the width of the material and then is spread over the surface. This method suffers the disadvantages of lack of control over the spread of the gel and of uneven distribution of the gel. This technique also tends to cover most of the pores of the top layer of the undergarment, the top layer being that layer which is next to the wearer""s skin. This method of application, therefore, also tends to interfere with the absorbency of the undergarment, resulting in a less effective and less comfortable product.
In view of the foregoing background, the present invention provides an apparatus and associated methods for applying a gel in a uniformly controlled pattern onto a material moving on a production line. The gel is applied in a pattern that allows the deposition of a sufficient quantity of gel to produce the desired effect when the undergarment is worn but that does not reduce the absorbency of the undergarment. The present invention thereby advantageously provides for manufacturing a disposable undergarment which is more comfortable for the skin of the wearer through the application of a gel, while maintaining the high absorbency of the undergarment.
More particularly, the present invention provides an apparatus for applying a gel onto a material moving on a production line for the production of disposable undergarments. The apparatus preferably has a supply of gel, gel delivering means for delivering the gel in a predetermined and uniformly distributed pattern to the sheet of material, and gel delivering control means positioned in fluid communication with the supply of gel and the gel delivering means for providing a variably controlled flow of the gel through the apparatus and onto the material at a rate responsive to the rate of travel of the material on the production line.
The supply of gel is preferably held in a cylindrical container positioned in fluid communication with the gel delivering means and the gel delivering control means. Because the present invention provides the advantage of heating the gel only at delivery through the gel delivery means, the container is not heated but is held at room temperature to avoid undue evaporation of the gel. The relationship of the gel supply container to the other components of the apparatus of the present invention is best shown in FIG. 1.
The gel delivering means preferably includes an applicator shoe, simply known in the art as a xe2x80x9cshoexe2x80x9d, having a body generally rectangular in shape and which includes an inlet conduit for receiving the gel therein, a chamber connected to the inlet conduit for distributing said gel, a plurality of spaced-apart outlet conduits each extending from the chamber so that the gel is delivered therefrom onto the sheet of material in a pattern of substantially parallel lines. The body of the shoe has a lower surface and a groove extending along a slanted portion of that lower surface at the proximal end of the body of the shoe, the plurality of spaced-apart outlet conduits extending from the chamber to the groove for delivering the gel therefrom. The groove provides the present invention with a further advantage by acting as a pooling area for the gel as it is squeezed out from the plurality of spaced-apart outlet conduits, allowing the gel to flow smoothly and without the formation of globs that would fall onto the material, interfering with the proper deposition of the gel pattern on the material. The shoe has a heater to warm the body of the shoe and thereby promote fluidity of the gel at delivery onto the material. The lower surface of the body of the shoe also includes a horizontal portion which abuttingly overlies the material on the production line as it moves thereon and serves to prolong the warming of the gel after delivery and to allow better absorption of the gel by the material.
The gel delivering control means preferably includes a variable speed pump for conveying the gel through the apparatus and a pump controller connected to the pump for providing regulation of the pump. A further advantage provided by the present invention is gel delivering control in a manner responsive to the rate of movement of the material on the production line. The variable speed pump may be any one of various devices known and used in the art for delivering a measured volume at a given rate, including a gear pump or a peristaltic pump.
The present invention also advantageously provides methods of applying a gel onto a material moving on a production line. A method preferably includes supplying the gel, delivering the gel onto the material in a uniformly distributed pattern, and variably controlling delivery of the gel at a rate related to the predetermined rate of travel of the material. The method also includes delivering the gel onto the material at a rate responsive to the predetermined rate of travel of the material on the production line. The method additionally includes the step of heating the gel during delivery, thereby to reduce the viscosity of the gel and promote controlled delivery.
Another method of applying a gel onto a material moving on a production line according to the present invention includes supplying the gel to a shoe, heating the shoe and delivering the gel from the shoe onto the material moving on the production line. The method further includes the steps of delivering the gel in a uniformly controlled pattern, wherein the rate of delivery is variably controlled responsively to the predetermined rate of travel of the material on the production line.
Yet another method of applying a gel onto a material moving on a production line according to the present invention includes the steps of providing a shoe having an inlet conduit for receiving the gel therein, a chamber connected to the inlet conduit for distributing the gel, a plurality of spaced-apart outlet conduits each extending from the chamber so that the gel is delivered therefrom onto the material in a uniformly distributed pattern and providing a delivery controller positioned in fluid communication with the shoe, for variably controlling flow of the gel to the inlet conduit of the shoe and therefrom onto the material at a rate responsive to the predetermined rate of travel of the material.
Having thus summarized the present invention, a more detailed description will now be provided so that those skilled in the art may more fully appreciate its advantages.